Residual Stress of Silicon Films Deposited by Lpcvd From Silane

Abstract

AbstractIn this paper, amorphous, semi-crystalline and polycrystalline silicon films have been deposited by low pressure chemical vapour deposition (LPCVD) from silane SiH4 by ranging the deposition temperature from 555 to 635°C and the total pressure from 100 to 300 millitorrs. Films residual stresses have been determined thanks to the formula of Stoney by measurements of the wafer curvature before and after removal of the back side deposition. The influences of the different deposition parameters are reported and major stress variations are evidenced. By studying the effects of a 600°C crystallisation anneal and by comparing them to those observed for amorphous silicon films deposited from disilane Si2H6, compressive and tensile stresses are respectively related to “surface” and “volume” crystallisation phenomena. The different stress values of amorphous and polycrystalline silicon have been estimated and, according to these results, solutions are finally proposed in order to have a real control of residual stress into silicon depositions and to obtain low stress (σ ≈ 0) polysilicon films.